1. Field of the Invention
This invention relates to a light receiving device used in an image forming apparatus such as a laser beam printer or a laser copying apparatus for scanning with a light beam such as a laser beam and effecting image formation or a measuring machine such as a bar code reader or a laser measuring machine, and to an image forming apparatus using the light scanning device.
2. Related Background Art
As a light scanning device for scanning with a light beam such as a laser beam, a device in which a rotational polygon mirror is rotated to scan with a light is widely used. Heretofore, this rotational polygon mirror was incorporated into a molding assembled integrally with a driving unit, and mounted on a predetermined position on a support plate.
This state is shown in FIGS. 15 and 16 of the accompanying drawings. As shown in FIG. 15 of the accompanying drawings, a rotational polygon mirror 2 is assembled integrally with a driving unit 7, and a scanner comprising the rotational polygon mirror 2 and the driving unit 7 is set in a mating hole 9 in the support plate 4 of FIG. 15 and held by a keep plate.
As shown in FIG. 16, a rotary support shaft 10 is supported by bearings 12 which in turn are held by a holding member 17 which is adhesively secured to another member.
In the conventional construction wherein the rotational polygon mirror is incorporated onto the support plate 4, in order to maintain the position of the rotational polygon mirror, particularly, the position of the rotary support shaft, with high accuracy, it has been necessary to comply with numerous requirements such as the coaxiality of the mating hole 9 with the rotational polygon mirror and the mountability of the rotational polygon mirror onto the support plate, and such works have required cumbersomeness and skill which have hampered mass-productivity, the great number of parts used has also led to a problem that 20 it is difficult to maintain a high dimensional accuracy and the optical performance is liable to become irregular. Also, where such a construction is used in a laser beam printer, it has sometimes been the case that images are disturbed or detection of the beam becomes impossible.